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Chapter II - RRL - rrl for thesis initial draft (not final)
Civil Engineering (BSCE 01)
Ateneo de Davao University
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CHAPTER II
REVIEW OF RELATED LITERATURE
3D printers are getting more and more common these past few years. The use of 3D printers has become more accessible and cheaper. While it is a good thing that 3D printers are getting cheaper and more obtainable by the masses, the environmental impacts of cannot be ignored. The concept of 3D printing generates a lot of wastes, not only is waste produced during failed prints, but successful prints, especially complex ones would produce wastes since to have successful prints, it is necessary to print accompanying supports for the model that would then be cast off after the model is printed. Waste generation is not only present during printing, filaments themselves can also become waste when improperly stored. This section provides recent literature, internationally and locally, related to wastes, specifically that of PLA (Polylactic Acid) and PETG (Polyethylene Terephthalate Glycol) and their impact to the environment, and also the literature related to the use of plastics as substitute to the aggregates for concrete.
2 3D Printing 3D printing is a technology that allows user to create 3-dimensional, tangible objects through the successive addition of materials [1]. This involves the layer-by-layer fabrication of solid objects that were designed from computer-aided design (CAD) drawing. The type of 3D printer that this study would focus on is the Material Extrusion type, specifically the Fused Deposition Modelling (FDM). The most common type of materials for this kind of 3D printing are Polylactic Acid (PLA), Polyethylene Terephthalate Glycol (PETG), and Acrylonitrile Butadiene Styrene (ABS). This method involves heating and extruding the thermoplastic filament.
2 Waste from 3D Printing By introducing a new way to manufacture with plastic materials, 3D printing has created a new source of plastic pollution [2]. The usage of prototyping and 3D printers, generally known as additive manufacturing technologies (AMT), has been expanding quickly in recent years. Fabrication Laboratories (FAB LABs) are small-scale laboratories that give the public access to tools for them to fabricate their innovations. These laboratories promote tinkering and <freedom to fail= for the makers by providing them an avenue wherein they can realize their prototypes. Unsurprisingly, a portion of materials that they provide will turn into wastes [3]. The study of Velasco et al. found that all the FAB LABs that were part of their sample size have 3D printers as seen on Figure 1. Some of the machines used by the FAB LABs that were part of the sample size
uses plastic as their medium of production, this is especially true for the case of 3D printers. This would then generate plastic wastes.
Figure 1. Summary of available machines and equipment in different Philippine FAB LABs
2 Polylactic Acid (PLA)
Polylactic Acid (PLA) is one of the most widely used form of bioplastic globally [4]. It is produced from the fermentation of starch present in sugarcane and corn. Due to PLA being somewhat biodegradable, there are many options for its end-of-life (EOL) stage. One of them is to decompose under industrial composting facilities conditions [5]. The issue with this is that there are still uncertainties with regards to the end-of-life (EOL) of this type of plastic. This is since the already existing waste management systems for plastics are yet to be adjusted for PLA. Another thing to note about PLA is that there are degradation stability issues regarding PLA with soil under ambient temperatures, the risk of environmental contamination is still present. The process of producing PLA has lesser number of emissions and industrial wastage compared to that of ABS [6]. The study of Aravind Raj et al. shows that a 3D printed object made with PLA has a 6% weight reduction when buried under landfill. This result supports the idea that PLA decomposes under ideal soil conditions. There are also certain bacteria that can help in decomposing PLA.
RPA is more durable compared to that of natural lightweight aggregate. Application of such concrete may be suitable in cases where there is exposure to chemical attack (marine or coastal areas), and non-structural concrete (utility trench backfill or low-rise housing).
2 The Use of 3D Printing for Reinforcement
The use of 3D printing is prevalent in studies that involves using geopolymers. 3D printing is suitable for geopolymers used in large-scale building with complex shapes [13]. The study of Santana et al. has findings that show that the shape or geometry of the printed mesh will affect the behavior of the composite, another is that PETG has chemical resistance against alkaline environment, this is highly useful when PETG is used in combination with concrete. The study conducted by Godek et al. involved 3D printing actual flexural reinforcements using PLA filament. The researchers used two different thickness for the reinforcement and the presence (or absence) of protrusions. It was found that the reinforcements printed with protrusions resulted in a better flexural strength and deflection capabilities.
References
[1] N. Shahrubudin, T. Lee and R. Ramlan, "An Overview on 3D Printing Technology: Technological,
Materials, and Applications," Procedia Manufacturing, no. 35, pp. 1286-1296, 2019. [2] A. Rodriguez-Hernandez, A. Chiodoni, S. Bocchini and R. Vazquez-Duhalt, "3D Printer waste, a new source of nanoplastic pollutants," Environmental Polution, vol. 267, p. 1, 2020. [3] L. C. Velasco, M. J. Burden, M. J. Satiniaman, R. B. Uy, L. V. Pueblos and R. Gimena, "Preliminary Assessment of Solid Waste in Philippine Fabrication Laboratories," AIMS Environmental Science, vol. 8, no. 3, pp. 255-267, 2021. [4] E. R. Ghomi, F. Khosravi, A. S. Ardahaei, Y. Dai, R. E. Neisiany, F. Foroughi, M. Wu, O. Das and S. Ramakrishna, "The Life Cycle Assessment for Polylactic Acid (PLA) to Make It a Low-Carbon Material," Polymers, vol. 13, no. 1854, 2021. [5] D. Maga, M. Hiebel and N. Thonemann, "Life Cycle Assessment of Recycling Options for Polylactic Acid," Resources, Conservation & Recycling, vol. 149, pp. 86-96, 2019. [6] S. A. Raj, E. Muthukumaran and J. K, "A Case Study of 3D Printed PLA and Its Mechanical Properties," Materials Today, vol. 5, pp. 11219-11226, 2018. [7] K. Durgashyam, M. I. Reddy, A. Balakrishna and K. Satyanarayana, "Experimental investigation on mechanical properties of PETG material processed by fused deposition modeling method," Materials Today, vol. 18, pp. 2052-2059, 2019.
[8] Husnah, D. R. Basri, P. Ningrum and A. Zaki, "The Effect of PET (Polyethylene Terephthalate) Plastic on Lightweight Concrete," Advances in Engineering Research, vol. 1999, 2020.
[9] M. J. Islam, M. S. Meherier and A. R. Islam, "Effects of waste PET as coarse aggregate on the fresh and harden properties of concrete," Construction and Building Materials, vol. 125, pp. 946-951, 2016.
[10] S. T. Chelve, S. Sivakumar, M. R. Kumar, G. Shanmugaraja and M. N. V. Priyan, "Effect of Polythylene GLycol as Internal Curing Agent in Concrete," International Journal of Innovative Research in Science, Engineering and Technology, vol. 6, no. 3, 2017.
[11] K. Singh, "Mechanical properties of self curing concrete studied using polyethylene glycol-400: A- review," Materials Today: Proceedings, vol. 37, pp. 2864-2871, 2021.
[12] F. K. Alqahtani, G. Ghatora, M. I. Khan, S. Dirar, A. Kioul and M. Al-Otaibi, "Lightweight Concrete Containing Recycled Plastic Aggregate," International Conference on Electromechanical Control Technology and Transportation, 2015.
[13] H. A. Santana, N. S. A. Junior, D. V. Ribeiro, M. S. Cilla and C. M. Dias, "3D printed mesh reinforced geopolymer: Notched prism bending," Cement and Concrete Composites, p. 116, 2021.
[14] E. Godek, S. Sevik and U. O. Ozdilli, "A Study on Flexural Behavior of Cement Paste Reinforced by Using 3D-Printed Polylactic Acid-Based Reinforcement," International Icontech Symposium on Innovative Surveys in Positive Sciences , 2020.
Chapter II - RRL - rrl for thesis initial draft (not final)
Course: Civil Engineering (BSCE 01)
University: Ateneo de Davao University
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